I had keys to one of my houses before completion as I had to have some electical and gas work done before I could move in. I also camped there the night before I should have moved in with my cats and a sun lounger as removal company was arriving at silly o'clock in the morning.
However, the nephew of the person who's house it was went balistic that I was in before he handed me the key which was silly because the sale had to go through It was a single transaction and I had paid to have work done on the house. Nasty, scary man